so ive been messing around with this thing for about three months on and off and last night i actually heard a qso on it which felt pretty surreal honestly. its based loosely on the norcal 40a design but i swapped out a few parts because i couldn't source the original ones without waiting six weeks for a shipment from overseas.

the audio is a little hum-y and im pretty sure its a grounding issue somewhere on the board but its definitely receiving. picked up a station in ohio last night and im in western pennsylvania so thats not bad for a chunk of ugly perfboard and whatever junk i had in my parts bin. used an NE602 for the mixer which i know some people hate but i had like eight of them laying around so whatever.

the main thing i keep running into is the audio amp stage just seems kinda weak. im running it into a set of old computer speakers and it works but i feel like the gain isnt where it should be. anyone done much with LM386 based stages after an NE602 and had luck tweaking the gain without introducing a ton of noise? ive tried bumping the cap between pins 1 and 8 and it helps a little but then the hum gets worse

the hum getting worse when you crank the gain on the 386 is pretty much expected, that chip picks up everything. thing i found that helped a lot was bypassing the supply rail really aggressively right at the chip — like a 100uf electrolytic and a 0.1uf ceramic both physically as close to the pins as you can get them. also if youre running it off anything wall wart related just switch to a battery for testing first just to rule that out, you might be surprised.

NE602 gets a bad rap but honestly for a first receiver its totally fine, the sensitivity on 40 is more than enough for what you need. the noise figure isnt great but if youre not chasing weak signal stuff it wont matter. did you put any filtering between the 602 output and the 386 input? a simple LC lowpass helps a ton with images bleeding through into the audio range.

nice work getting it on the air, ohio from western PA on a homebrew direct conversion is solid. i built something similar about two years ago and the hum drove me insane for weeks, turned out one of my ground connections on the volume pot was floating and i just hadnt noticed it. worth checking all your mechanical grounds on any panel hardware before going too deep into the circuit itself.